Stitch for elastic netting

ABSTRACT

The present invention provides an improved system of stitching for forming a casing of tubular netting, in which the casing comprises circumferential elastic members formed from at least one continuous spiral or a plurality of separate circular loops, and longitudinal members formed from a plurality of chain stitches interconnecting adjacent loops of the spiral or separate loops of the circumferential elastic members, resulting in a net-like appearance, the longitudinal chain stitches being attached to the circumferential elastic members such that, at each connection point of the chain stitching to an elastic member, a first chain stitch is attached to the elastic member and a further pair of chain stitches is attached to the elastic member and spaced either side of the first chain stitch such that, when the first and further pair of chain stitches are stretched, the first chain stitch is caused to pull on the section of the elastic member located between the further pair of chain stitches such that elastic deformation of the elastic member in the direction of the stretch occurs.

BACKGROUND

This invention relates to an improved tubular net for food products, andin particular relates to an improved stitch for tubular net or netting.

The present invention may find many applications, and these applicationsmay not be limited to the food industry. However, for easy description,the invention will be described in relation to its application for usein the food industry.

In the following description, the terms "casing", "food product" and"netting" shall have the following meanings:

    ______________________________________    "casing"     any synthetic or natural tubular material                 used in the processing of food products                 such as meat products,    "food product"                 any fresh or processed food products, and                 in particular fresh or processed meat                 products, and    "netting"    any knitted, woven, extruded or otherwise                 manufactured packaging netting which is                 elasticated, rigid or laterally                 extendible.    ______________________________________

In the manufacture of food products, and in particular in respect of themanufacture of meat products, natural or artificial casings in the formof elongated tubes are normally either pumped full of meat from amachine specifically designed for the purpose, or have portions of meatplaced within the tube prior to either a cooking or a curing processtaking place.

In some cases, machines dealing with minced meat products use a feedmechanism for injecting meat through a delivery tube or injection hornwhere the casing is shirred onto the external surface of the deliverytube. A clip or other closure means is placed over the end of thecasing, and a quantity of meat is then injected into the casing.Depending on the desired length of the meat product, the process isinterrupted at various stages so that clips or twists may be applied toform separate and individual meat product portions.

In addition, whole meat portions may be inserted within tubular casingand, in this instance, stuffing tubes or horns are also used whichenable the tubular casing to be stretched, whereupon meat portions canbe readily introduced within the tubular casing.

In some cases, artificial skins such as collagen-based casings orfibrous casings have a tubular net or netting placed over the outside ofthe collagen once the food product is located within the casing.Alternatively, the food product may be inserted directly within thenetting without the use of any inner casing.

In many instances, the netting is used primarily for decorative effectand remains in place prior to consumption of the food product. However,in addition to providing a decorative effect, the netting, if properlysized, can be used to produce a surface pattern effect. In thisinstance, the longitudinal and circumferential members of the net applya force to the surface of the meat product and, provided that thesurface of the food product is sufficiently resilient, then the nettingwill protrude into the surface of the food product. This results in aquilt-like surface pattern, where the circumferential and longitudinalmembers press into the surface of the food product so that the foodproduct bulges outwardly within the square or rectangle formed by thelongitudinal and circumferential members.

In addition to the appearance, it is also desirable, particularly inrelation to the cooking or curing process, to maintain a desirableshape, and to apply constant compressive force to the meat productduring the cooking or curing process. The constant pressure ensures thatair pockets do not readily form within the meat, as this may lead tospoilage. It is also desirable to ensure that, particularly during aprocess where the meat product is hung to cure, no elongation orstretching of the meat product occurs.

In some instances, during a curing process, the weight of the meatproduct can cause the netting to stretch, thus resulting in a conical ortapered section from the hanging point to the beginning of the meatproduct. In many instances, depending on the type of the meat product, asmall conical section of meat can be formed at the upper end. Thisparticular section tends to be unsightly when the netting is removed,and is normally cut away and wasted.

This problem results from the fact that elastic netting is normallynon-elastic in the longitudinal direction. Only the circumferentialmembers, which form a continuous spiral, are normally formed fromelastic material. The longitudinal members are formed from conventionalchain stitching. Apart from the normal stretch which results from theknitting process, the netting is generally inextensible in thelongitudinal direction. Accordingly, as there is no longitudinalelasticity, stretching and thinning at the upper end of the netting willoccur during the curing process.

SUMMARY AND OBJECTS OF THE INVENTION

Therefore, it is an object of this invention to overcome theabovementioned problem and to provide netting which is elasticallyextensible in the longitudinal direction.

In its broadest form, the invention comprises an improved stitch forforming a casing of tubular netting, in which the casing comprisescircumferential elastic members formed from at least one continuousspiral or a plurality of separate circular loops, and longitudinalmembers formed from a plurality of chain stitches interconnectingadjacent loops of the spiral or separate loops of said circumferentialelastic members, resulting in a net-like appearance, the longitudinalchain stitches being attached to the circumferential elastic memberssuch that, at each connection point of the chain stitching to an elasticmember, a first chain stitch is attached to the elastic member and afurther pair of chain stitches is attached to the elastic member andspaced either side of said first chain stitch such that, when said firstand further pair of chain stitches are stretched, the first chain stitchis caused to pull on the section of the elastic member located betweensaid further pair of chain stitches such that elastic deformation of theelastic member in the direction of said stretch occurs.

The yarn used to form the stitches may comprise a single filament, orinstead may be a multi-filament yarn.

In a preferred embodiment, the first chain stitch extends to one side ofthe elastic member to which it is attached, along the longitudinal axisof the casing, and the further pair of chain stitches extends to theopposite side of said elastic member.

The centre pull effect of the first chain stitch between the furtherpair of chain stitches results in the pair of stitches separating fromeach other (rather than being drawn together), with the elastic memberbeing stretched into a U-shape. Although only a small amount ofdeformation is achieved, the deformation of each of the loops of thecircumferential members along the length of the netting will result inquite a considerable elastic extension. It would normally be expectedthat a conventional netting will extend by approximately 10%. It hasbeen found that the netting of the abovedescribed invention will in factextend by up to 50%.

The important feature is of course that the extension is elastic, whichresults in considerable longitudinal force being applied to any meatproduct placed within. This constant longitudinal pressure prevents orreduces any localised thinning of the meat product, particularly in theupper region of the netting adjacent to the suspension point.

The important aspect of the invention is deformation of the elasticmember in the direction of the longitudinal axis of the tube of netting.This may be achieved in numerous means, such as staggering thelongitudinal stitches between adjacent loops of the circumferentialmembers so that the longitudinal stitches do not form a continuous linealong the longitudinal axis of the casing, but are offset with respectto one another so that the necessary deformation of the elastic memberoccurs. Alternatively, the longitudinal members may in fact besubstantially in line, but a pair of chain stitches to one side of theelastic member may form substantially a V-shape so that the stitches arespaced either side of said first chain stitch.

Preferably, a stitch or knot is formed at the point where the firstchain stitch attaches to the elastic member. The knot tightens uponlongitudinal tension being applied, and prevents any shortening ormovement of threads associated with the pair of chain stitches to eitherside. This in turn ensures that the first chain stitch will pull againstthe elastic member rather than transferring any of the longitudinalforce to the pair of chain stitches at either side.

In addition it has been found that stitching according to this inventionproduces a product that feels soft to the touch as a result of being amuch bulkier knit. This is important in respect of repetitive manualhandling of the product in that it is easier to use over extendedperiods of handling.

A further problem with the manufacture of netting is the productionrate. Clearly, it is desirable to achieve the highest possibleproduction rate for a given product. However, one of the main factorslimiting the production rate is the speed at which the knitting machineoperates. Clearly, for a given design of stitch or orientation ofnetting, there is a maximum speed at which a machine may operate, whichof course results in a maximum production rate that cannot be increased.

Accordingly, it is a further object of this invention to provide a meanswhereby the production rate of netting can be increased.

In this further aspect of the invention, the netting comprises two ormore elastic threads forming two or more separate circumferentialspirals.

It has been found that knitting machines commonly used to produce thenetting are able to produce longitudinal stitches at quite high rates.The factor that dictates the speed at which these longitudinal stitchesare formed is the rate at which the circumferential members areintroduced into the netting. Accordingly, by introducing more than onecircumferential spiral into the netting at a time, the rate can beeffectively doubled or trebled by increasing the circumferential membersto two or three separate spiral-forming threads.

BRIEF DESCRIPTION OF THE DRAWING

In order for the invention to be more readily understood, the inventionwill now be described with respect to a preferred embodiment, which isillustrative but not restrictive of the present invention. Thispreferred embodiment is illustrated in the accompanying representationsin which:

FIG. 1 shows an expanded view of a connection point between thelongitudinal stitches and the elastic member,

FIG. 2 shows the stitches illustrated in FIG. 1 under longitudinalstress or tension, and

FIG. 3 is a perspective view of a section of the tubular casing.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

As seen in FIG. 1, a first chain stitch 10 is attached to an elasticmember 11 and extends transversely to one side of elastic member 11. Apair of chain stitches 12 are also attached to the elastic member 11 andextend transversely to the opposite side of elastic member 11. The pairof chain stitches 12 are spaced either side of the first chain stitch10. A knot 13 is formed which, when placed under longitudinal stress ortension, acts to fix the first chain stitch 10 with respect to theelastic member 11. This knot prevents any tensile forces beingtransferred via the thread to the pair of chain stitches 12 that wouldcause the pair of chain stitches 12 to slide together.

As seen in FIG. 2, when placed under tension, the knot 13 tightensaround the elastic member 11 and the first chain stitch 10 iseffectively tied to the elastic member. Therefore, although the stitchesare formed from one continuous length of thread, the tension is nottransferred to the pair of chain stitches 12. Accordingly, they remainin place either side of the first chain stitch 10, which in turn resultsin the elastic member 11 between the pair of chain stitches 12 beingpulled into a U-shape. Accordingly, the first chain stitch 10 pulls awayfrom the pair of chain stitches 12 under elastic tension and, althoughthe extent of movement is minor, the cumulative effect along the lengthof the netting will result in quite significant extension. The extensionis of course elastic, and therefore a longitudinal compressive forcewill be applied while the netting remains in an extended form.

It has been found by the Applicant that the particular type of stitchillustrated in FIGS. 1 and 2 is ideally suited to use with multiplethreads forming the circumferential members. Accordingly, the stitchesillustrated in FIGS. 1 and 2 may be used with two or more separatethreads forming the circumferential spirals.

FIG. 3 is a perspective view of a section of tubular casing 14,incorporating the system of stitching shown in FIGS. 1 and 2.Circumferential elastic members 11 and longitudinal members 15, formedfrom chain stitches 10 and 12, combine to form a netting product whichis elastically extensible in the longitudinal direction.

As will be seen from the above description, the invention provides asignificant improvement over known inextensible netting or net casings.This will provide a significant advantage in respect of the productionof certain meat products.

While the present invention has been described in terms of a preferredembodiment in order to facilitate better understanding of the invention,it should be appreciated that various modifications can be made withoutdeparting from the principles of the invention. Therefore, the inventionshould be understood to include all such modifications within its scope.

I claim:
 1. An improved stitch for forming a casing of tubular netting,in which the casing comprises circumferential elastic members formedfrom at least one continuous spiral or a plurality of separate circularloops, and longitudinal members formed from a plurality of chainstitches interconnecting adjacent loops of the spiral or separate loopsof said circumferential elastic members, resulting in a net-likeappearance, the longitudinal chain stitches being attached to thecircumferential elastic members such that, at each connection point ofthe chain stitching to an elastic member, a first chain stitch isattached to the elastic member and a further pair of chain stitches isattached to the elastic member and spaced either side of said firstchain stitch such that, when said first and further pair of chainstitches are stretched, the first chain stitch is caused to pull on thesection of the elastic member located between said further pair of chainstitches such that elastic deformation of the elastic member in thedirection of said stretch occurs.
 2. An improved stitch according toclaim 1 wherein said first chain stitch extends to one side of theelastic member to which it is attached, along the longitudinal axis ofsaid casing, and said further pair of chain stitches extends to theopposite side of said elastic member.
 3. An improved stitch according toclaim 1 or claim 2, wherein said first chain stitch and said furtherpair of chain stitches are offset with respect to each other, ratherthan forming a continuous line along the longitudinal axis of saidcasing.
 4. An improved stitch according to claim 1 or claim 2, whereinsaid further pair of chain stitches forms substantially a V-shape withthe stitches spaced to either side of said first chain stitch.
 5. Animproved stitch according to any one of claims 1 to 4, wherein a stitchor knot, which tightens upon application of tension or stress in adirection transverse to the longitudinal axis of said elastic members,is formed at the point where said first chain stitch attaches to theelastic member.
 6. An improved stitch according to any one of claims 1to 5, wherein said circumferential elastic members comprise two or morecontinuous elastic threads forming two or more separate circumferentialspirals.
 7. An improved stitch according to claims 1 or 2, wherein thecasing is a casing for a food product.
 8. An improved stitch accordingto claim 7, wherein the casing is a casing for a meat product.